Current practices in the management of broken bones employ a broad spectrum of mechanical variables in their treatment. To present there have been no controlled experimental studies which quantitate the strength of bone as a function of time and compare the effects on different quantified mechanical variables on rate of fracture healing. In this study, under standard operative techniques the tibial shafts of the tibiafibula of adult male rabbits were osteotomized. With a specially constructed spring calibrated compression clamp, a 3.5 kp was applied to one tibia-fibula, and a 2 kp load to the other tibia- fibula. A 1.5 kp cyclical load was then added to the 2 kp load. The healing is then monitored as a function of time. At the end of the healing interval the bones are tested for stiffness, maximum torque, maximum angulation, and energy absorption to failure. Tissue is studied histologically so that the "strength" can be compared with radiologic and histologic characteristics. Other aspects of this study include evaluation by polarized light microscopy, electron microscopy, and tetracycline labeling. This study will provide information as to what may be the more efficient mechanical variable to apply in order to have a healing fracture be as strong as possible as soon as possible.